Are people more likely to risk an HIV infection with sex partners they meet online as compared to those whom they meet offline? This question has been the subject of research since the late 1990s in several post-industrialized countries. This paper presents the results of a study conducted in Germany in 2006. A link to an anonymous, self-administered online questionnaire was posted on four dating websites for heterosexual men and women and on four dating websites for men who have sex with men. Of the 5,050 respondents included in the analysis, 76 per cent were men who reported sexual contacts in the previous twelve months exclusively with other men; 11 per cent could be classified as bisexual men (sexual contacts with men and women), and 11 per cent as heterosexual men (sexual contact with women only).. Two per cent of all respondents were women; because of the small number of respondents this group was not further stratified in the analysis. Finding persons with similar interests was the most frequently expressed positive aspect of dating websites (78% among homosexual men, 80% among bisexual men, 74% among heterosexual men, and 73% among women). This did not necessarily mean similar sexual interests: 22 per cent of the women, 12 per cent of the homosexual men, 6 per cent of the bisexual men, and 9 per cent of the heterosexual men claimed they had not been looking for sex partners during their visits to the sites in the previous twelve months. Many respondents reported being unsuccessful in finding a sex partner online: 18 per cent of the women, 21 per cent of the homosexual men, 24 per cent of the bisexual men, and 45 per cent of the heterosexual men. While during the previous twelve months half of the homo- and bisexual men found most (if not all) of their sex partners on the Internet, the respective proportions were 39 per cent among heterosexual men, and 67% in the small group of female respondents. Taken together, heterosexual men were the least successful in finding sex partners on the Internet. Regular use of condoms for every anal or vaginal intercourse was reported by 55 per cent of the homosexual men, 47 per cent of the bisexual men, 38 of the heterosexual men, and 34 per cent of the women. However, regarding unprotected anal or vaginal intercourse with a sex partner of unknown or discordant HIV serostatus, the proportions among the different subgroups were very similar (homosexual men: 27%; bisexual men: 31%; heterosexual men: 26%; women: 27%). The risk of transmitting a known HIV infection to sex partners was only present among homosexual (8%) and bisexual (1%) men, primarily because only respondents from these two subgroups identified as HIV-positive. For the large majority (83-86%) of men, HIV risk behaviours are the same, regardless if sex partners are met online or offline.